If you use the Picture Keeper mobile app, you can request deletion yourself: open the app and go to Settings › Account › Request Account Deletion. Deleting your account removes your email address and other account information from our systems.
If you don't have the mobile app, contact our support team and tell us the email address the account uses; we'll process the deletion for you.
The files on your drive are not affected. Everything backed up to your Picture Keeper drive stays on the drive — the account is separate from the drive, and you can keep using the drive (and create a new account later) without it.